The 10 best Prime Day mattress deals from Walmart, Casper, Leesa, Purple and more

There are so many factors in getting a good night’s sleep — your mindset, your overall health, your evening habits, your mattress. While each plays an important role, sometimes a new mattress is the quickest route to better ZZZs. Especially if it's been a while since you updated (and especially if your back hurts when you wake up in the AM: that's a red flag for a worn out mattress).

A mattress is definitely an investment, but as it turns out, there's no better time to buy one. Amazon's second Prime Day is going strong — a surprise bonus ahead of the holiday rush — and tons of bestselling, top-rated mattresses are majorly marked down. And believe it or not, Amazon is not the only place to shop. Because retailers are overstocked and looking to move merch, there are lots of great spots to score a top-quality mattress on sale today.

Not sure where to even begin? We've got you. To get the right specs, we talked to two doctors. Then, applying their criteria, we scoured the sales and pulled together a list of deals for you.

What did the docs have to say?

“A better mattress absolutely can help with sleep,” Christopher Winter, M.D., of Charlottesville Neurology and Sleep Medicine and author of the book The Sleep Solution: Why Your Sleep Is Broken and How to Fix It, tells Yahoo Life.

There are a few specific signs that it’s time for a mattress upgrade, according to Winter:

• You’re moving around a lot at night. “A lot of times, pain or discomfort makes you move a lot to try to get comfortable,” Winter says. You might not even realize this is happening. Check out the status of your sheets in the morning—if they’re all bunched up or twisted, it’s a good sign you were tossing and turning. Or, if you sleep with a partner, Winter recommends asking if they’ve noticed you moving around at night.

• You’re sore in the morning. The wrong mattress can put pressure on your hips, shoulders, and knees, causing stiffness and soreness in the morning, Winter says. “Soreness is a great way to find out if your mattress is supporting you the right way,” he says.

• You’re overheating. If you’re getting hot and sweaty at night, your mattress could be to blame. “Some mattresses that offer more support can sometimes make you feel hot,” Winter says. “Sweating in bed is a big thing people often put up with, but they shouldn’t.”

Winter recommends making a list of what you need—more joint support, a softer feel, a cooling environment—and looking for options based on that. If you have a partner, Winter suggests sitting down with them and making a list of the factors that are important to each of you in a mattress. “If they widely diverge, you probably want to look for a mattress that you can customize for each side,” he says.

Not sure what you need? Opt for a medium-firm option, Harrison A. Linder, M.D., pain management specialist with The Center for Interventional Pain Medicine at Mercy Medical Center in Baltimore, MD, tells Yahoo Life. ”They tend to be firm enough to offer support for back and front sleepers, but still offer some cushion for those that prefer to sleep on their sides,” he says.

And, if you have back pain, Linder says it's important to make sure your mattress offers the right support for you. "Just like trying to maintain good posture while standing and sitting, it is important to keep the components of the back — vertebral bones, intervertebral disks, and all associated ligaments — in healthy positions while sleeping," he says.

It's also a good idea to see how the mattress feels, Linder says. "This is not a simple case of 'one size fits all,'" he adds. (Most online mattress retailers have fantastic return policies, so you really can do a trial run before you fully commit.)

Here are a few options to get you started. Bonus: They are all on sale right now and they all have great return policies.

This popular Allswell mattress has temperature-regulating properties and individually wrapped coils to isolate body movements and prevent you from bothering your partner. It's even infused with antimicrobial copper particles to help keep you feeling cool as you sleep.

The Leesa Original Mattress is made with premium foams to help cool you off, contour to your body, and offer support for pressure points. You can try the mattress for 30 days and, if you decide it’s not a good fit, Leesa will pick it up from your place and refund the full purchase price. Right now all sizes of the Leesa Original Mattress are on sale, starting at $749 for a twin.

The hypoallergenic Purple Mattress is made from non-toxic materials, so you can feel good about what you're sleeping on. Its comfort core technology prevents bouncing while the 1,400+ built-in air channels help promote breathability. The mattress comes with a 10-year warranty, and you've got 100 nights to determine it it's a fit.

The Casper Original has a top layer of breathable foam with tiny holes to help move heat away from your body and keep you cool at night. A durable base offers support and prevents sinking and sagging. Casper offers a 100-night risk-free trial so, if you don’t like the mattress, they’ll pick it up, pack it up, and give you a full refund.

Made from a premium memory foam material, this ultra-comfortable mattress is designed to conform to your shape to provide custom support as you sleep. The twin-size mattress can support weights up to 250 pounds and all other sizes can support up to 500 pounds.

This Nectar mattress is packed with memory foam. It features a layer of gel memory foam to help distribute your weight and body heat, and another layer of adaptive memory foam for support. The mattress has nonstop airflow throughout its layers to help keep you feeling cool while you sleep. Nectar tops everyone in the trial department: They let you try out their mattress for an entire year and return it for a full refund if it doesn’t feel right.

Saatva’s hybrid innerspring mattress has a special Euro pillow top that’s more cushioned than standard mattress tops to keep you comfy at night. Saatva lets you choose between soft, medium, and firm options at the same price. The company also offers a 120-day trial and has a no-hassle return policy, if you ultimately decide this isn’t the mattress for you. All sizes of the Saatva Classic mattress are on sale.

Helix is incredibly soft to the touch and is made to increase airflow, helping you to stay cool at night. Wrapped coils help cradle your body for extra support while you sleep. Helix offers a 100-night sleep trial so, if you’re not in love after 100 days, you can send it back.

The Pod Pro is dual-zone, so you and your partner can find a temperature that’s right for each of you. It combines four layers of foam and an active grid that works to create the best level of comfort, support and temperature for a good night’s sleep. The Pod Pro can even adjust the surface temperature of the bed to wake you up gradually when it’s time. An app lets you control the settings and see how well you’re snoozing at night. Eight Sleep gives you 100 days to try it out and return it without paying shipping charges.

If you want to upgrade your mattress without breaking the bank, this Nap Queen option might be just what you're looking for. The mattress's polyurethane memory foam will contour to your shape to provide ergonomic support. Plus, it's made without any harmful chemicals. Even better, the mattress features a cooling gel to keep you from overheating.

Psst: If you're shopping for a mattress on Amazon, you need to be an Amazon Prime member to take advantage of the Prime Early Access deals. Here's how you can sign up for a free trial.

The reviews quoted above reflect the most recent versions at the time of publication.

See all of our Prime Early Access Sale coverage, here. Shop the top early Prime Day deals on Yahoo Life, get the best Prime Day tech advice on Engadget, learn about Prime Day trends on In the Know, and check out Prime Day car deals on Autoblog.